Several different types of blank stackers are used in the corrugated paperboard industry, one type of which is used to stack folded, flat carton blanks as they are discharged from a blank folding and gluing machine. Prior to stacking, the blanks have usually been printed, creased, slotted, glued, and folded as well understood by those skilled in the art. At this point, the blanks have been made into flat, collapsed folded boxes which can be later erected for filling of goods. The next step is to collect them in stacks to be tied into bundles for shipment to the ultimate user. The blanks are usually counted as they are stacked and the stacker (sometimes called a counter ejector) is adapted to discharge stacks of a predetermined number of blanks.
Counter-ejectors of the type to which this invention is directed form the stacks of blanks by receiving the advancing blanks one at a time beneath the stack. Examples of such machines may be found in Ward U.S. Pat. No. 3,744,649, Shields U.S. Pat. No. 3,203,561, and Nelson U.S. Pat. No. 3,834,290. A common characteristic of these machines is that the stack of blanks is formed from the bottom, that is, the blanks advance one at a time beneath the stack being formed. And, they simultaneously share a common problem which is that the blanks entering beneath the stack often hang up due to friction between them and the bottom blank of the stack. Such friction results from the frictional coefficient of the paper as well as the weight of the stack acting upon the blanks entering beneath the stack.
Besides hanging or jamming up in the stacker, which interrupts production, another problem is that the printing on the blanks, while usually dry at this point, is subject to scuffing due to sliding friction between the bottom blank of the stack and the blank entering. And, if the blank entering tends to hang up, the blank is scuffed on the bottom by the endless conveyor belts that advance the blanks beneath the stack. Accordingly, an object of the present invention is to provide a means for reducing jamups in carton blank stacking machines. Another object is to reduce scuffing of the carton blanks as they are stacked in such machines. These and other objects and novel features are generally accomplished by the invention, a summary of which appears below.